The important thing is the variable instanceName which define our collection.

Before testing, check the file app/code/Maxime/Jobs/Model/ResourceModel/Department/Collection.php and verify you have a line like :protected $_idFieldName = \Maxime\Jobs\Model\Department::DEPARTMENT_ID;

If not, you must add it. Now you can mass delete some elements !

Next step is practical exercises which repeats the 2 last units, but for the “Job” element.

I have change
“Training\ComputerGame\Model\ResourceModel\ComputerGame\Collection” to “Training\ComputerGame\Model\ResourceModel\ComputerGame\Grid\Collection”
but the system show error in grid list.
Class Training\ComputerGame\Model\ResourceModel\ComputerGame\Grid\Collection does not exist